1. Field of the Invention
The present invention relates to a method of manufacturing an array substrate and a method of manufacturing an organic electroluminescence (EL) display device having the array substrate.
2. Description of the Related Art
Recently, for example, an organic EL display device and a liquid crystal display device have been used as a display device. Since the organic EL display device does not require a backlight unit that is used for liquid crystal display devices, it can be thinned, lightened, decreased in power consumption, reduced in costs and achieved as a mercuryless one. Since, moreover, it is a self-luminous display device, it has the features of wide viewing angle and high-speed response. The organic EL display device therefore receives attention as a device for displaying moving images such as a television (TV) set as well as a device for displaying still images such as a notebook personal computer (PC), a monitor and a viewer.
The organic EL display device includes an array substrate. The array substrate has a glass substrate and a plurality of organic EL elements arranged in matrix on the glass substrate. Each of the organic EL elements forms one pixel and has an anode, a cathode opposed to the anode and an EL layer interposed between the anode and cathode. The EL layer contains an organic compound having a light-emitting function and can emit any one of red light, green light and blue light.
The interval between the anode and cathode is as narrow as about 1 μm. In the process of manufacturing the organic EL display device, a short circuit is likely to occur between the anode and cathode. This short circuit occurs when a foreign substance is interposed between the anode and cathode, when the EL layer comes off due to trouble with manufacture, or the like. A pixel to which the foreign substance is attached becomes unlit and cannot emit light. If a number of pixels are unlit, a display device greatly decreases in image quality and display quality and cannot be shipped as a product. It is thus necessary to repair the unlit pixels.
For example, Jpn. Pat. Appln. KOKAI Publication No. 2004-227852 discloses a method of repairing an unlit pixel. According to this method, a short-circuited portion between an anode and a cathode is irradiated with a laser beam to form a high-resistance region between them. The method lights an unlit pixel and accordingly the pixel functions as a normal one. The method allows a foreign substance to be removed from a pixel with a laser beam to thereby light the pixel.
Foreign substances vary in shape and size. In the prior art method, the rate of success in repair varies to cause both a case where an unlit pixel can be repaired and a case where it cannot be repaired. Since an unlit pixel is difficult to repair with efficiency, a display device cannot be manufactured with stability.
The present invention has been made in consideration of the above situation and its object is to provide a method of manufacturing an array substrate and a method of manufacturing an organic EL display device with stability to repair an unlit pixel with efficiency.